This invention relates to a load-responsive brake-force regulator for a vehicular hydraulic brake system, the static characteristics of which run radially and wherein the brake pressure supplied to the wheel brakes at the rear axle is regulated by the adjustment of the transmission ratio which is effected continually dependent on the instantaneous axle-load distribution by means of a balance beam, the one lever arm of which is linked to an actuating piston exposed to the master cylinder pressure while its other lever arm is linked to a control piston, with the control piston actuating a control valve arranged in the pressurized-fluid line leading from the master cylinder to the wheel brakes at the rear axle, and with the balance beam bearing upon two rollers held in a guide cage and adapted to move along a rail dependent on the instantaneous axle-load distribution by means of an actuating tongue disposed between the rollers, the one roller serving as a support for the balance beam and the other roller resting on the rail, with the two rollers being able to move with rolling contact on the balance beam and on the rail, respectively.
Such a load-responsive brake-force regulator is known from German Pat. No. Dt-AS 1,780,560. In the known brake-force regulator, two tension springs are provided urging, in the normal position, the guide cage against a stop secured to the housing. Thus, in the normal position, there is a defined position of the guide cage relative to the balance beam. However, if the actuating tongue moves as a result of an increase in the axle load, the guide cage is bound to move against the unilaterally acting force of the tension springs. As long as there is static-friction engagement between the rollers and the actuating tongue, between the one roller and the balance beam and between the other roller and the rail, the amount of displacement of the guide cage corresponds precisely to half of the amount of displacement of the actuating tongue. However, the case may be that this static friction is not fully present which may be due to vibrations or other causes. In that case, the actuating tongue is able to move between the rollers without there being a suitable displacement of the guide cage. As a result, the required proportional relationship between the change in the axle load and the brake-force distribution is lost.